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Quick start

1. Install the extension and sign in once with a free account.
2. Play a song in any tab (YouTube or anywhere with audio).
3. Click the Instrufilt icon, or press Alt+Shift+I.
4. Pick an isolation mode and set the Isolation slider.
5. Click Start isolating. The band drops out in real time; the singer stays.

The side panel is pinned to the tab you started it on. You can also right-click a page and choose “Isolate vocals on this tab”.

Isolation modes

Vocal + rhythm

The singer plus the centred kick, bass, and snare. Keeps a groove to lock to while you cover the harmony — the best starting point, and the default.

Vocal only

The singer alone, filtered clear of the rhythm section. The cleanest reference for the melody and phrasing, but there is no time feel — you are the whole band.

Lead line

A narrow band around the voice, for picking a melody out by ear. Thin on purpose.

The Isolation slider blends the isolated signal against the untouched mix. At 0% it is bit-exact passthrough, so you always have an honest A/B; at 100% you hear the maximum isolation the mode can give.

What to expect

Instrufilt separates the singer from the band with two estimators: one asks where each frequency is panned (lead vocals usually sit dead-center), the other asks whether the same energy was also there a bar ago— the band repeats itself; the singer doesn't. Both run in real time on your machine, which makes it fast and private, but it also means results depend on how a song was recorded and mixed. Some songs come out with the vocal floating clean over your playing; others separate less cleanly. We can't guarantee it works on everything.

Works best on

Standard studio stereo mixes with the lead vocal panned dead-center — which covers most pop, rock, hip-hop, and electronic releases from roughly the mid-70s onward.

Expect weaker results on

• Mono recordings or mono uploads — with no stereo separation, one of the two estimators has nothing to work with.
• Old hard-panned stereo (many 50s–60s records) where the voice sits in one speaker instead of the center.
• Live recordings and concert videos — the vocal bleeds into every microphone, plus crowd noise.
• Heavy vocal reverb or stereo delay — the dry voice is kept but its echoes live in the sides of the mix and thin out with the band.
• Phrases the singer repeats identically within a few bars — the repetition detector can mistake them for backing. This is the mirror image of how it works.
• Dense or heavily distorted mixes — the band and the voice overlap so much that some of the band always leaks through.

One deliberate quirk: Vocal + rhythm keeps the centred rhythm section on purpose, so the repetition detector is off in that mode — the rhythm section is the most repetitive thing in the mix and would be the first thing removed. Switch to Vocal only or Lead lineto hear the full separation. Use the Isolation slider to find the sweet spot between separation and sound quality, and check a song's community votes to see how well it worked for other players.

The lead sheet

While a song plays, the side panel shows a lead sheet: chord symbols above time-synced lyrics, with the current chord and the next change called out in a strip up top. Lyrics come from Karalyr (word-synced where it has them) and LRCLib.

Where the chords come from

Best source wins. When the song is a YouTube video and a ready-made chart exists — in Karalyr, the family's own chord database, or in Songle, AIST's music-understanding research service — Instrufilt fetches it. Only the video's address is sent; audio still never leaves the browser, and the panel credits “Chords: Songle (AIST)” whenever their data is shown. For everything else — about half of YouTube, all of Spotify, or with Online chords toggled off — chords are detected on your device from the audio itself.

Listening vs. Chart

On-device detection is real-time, so on the firstplay a chord is recognised slightly after it starts sounding — useless for playing along, and the panel doesn't pretend otherwise: chords appear dimmed and italic under a Listening badge while the chart is built. Every play after that shows the Chart: the whole lead sheet rendered up front, ahead of the playhead, re-decoded offline for accuracy and cached per song.

Transpose & capo

The ± buttons shift the written chords without touching the audio, so a capo'd guitarist reads the shapes they're actually playing. Accidentals follow the estimated key — Bb in a flat key, never A#.

Chord shapes

Tap the big current-chord readout to open fingering diagrams for the current and next chord — drawn the way guitarists expect (“C” looks like C, not like a barre shape halfway up the neck).

Learn the song

The song row carries two shortcuts: How to play ↗ searches YouTube for a tutorial on the current song and your instrument, and Tab ↗ opens the song on Songsterr.

Count-in

During intros and instrumental breaks the sheet shows the chords of the gap and a bar filling toward the next line, so you come back in on the downbeat.

How accurate are detected chords?

A fetched chart is millisecond-accurate, with 7ths, sus and slash chords. On-device detection is honest about being approximate: major and minor triads only, roughly 55–65% right on clean pop and rock, lower on dense, distorted, or live material. Relative major/minor confusion (C ↔ Am) is the most common error, and power chords make major/minor a coin flip. Chords below the confidence threshold are drawn with a dotted underline — check those first.

Settings

Everything lives in the side panel, and your choices are saved across sessions.

Isolation mode

Vocal + rhythm, Vocal only, or Lead line — see the modes above.

Isolation

0–100% blend between the untouched mix and the isolated signal. 0% is bit-exact passthrough.

Output level & Auto-level

Make-up gain from −6 to +18 dB, because an isolated vocal is quieter than the full mix. Auto-level rides it for you.

Mono

Collapses the output to mono — useful when practising on one speaker or checking what the isolation is doing.

Chords

Show or hide the chord tier of the lead sheet.

Online chords

Allow fetching ready-made charts (Karalyr, Songle) for the current song. Toggle off to stay fully local — on-device detection keeps working.

Rate the isolation

Did it work on this song? Answer with a thumbs up or thumbs down and an optional comment, tied to the song and the active mode. Revisit a song and the panel pre-fills your previous vote so you can change it.

Community votes

The panel shows how many people liked and disliked the isolation on a song, so you can tell before committing to a practice session whether it's a good candidate. Only aggregate counts are shown — individual votes stay private, and voting yourself helps everyone after you.

Practice stats & badges

While you're signed in, Instrufilt records which songs you practise and for how long, so your account page can show your stats: total practice time, sessions, unique songs, a per-mode breakdown, and your most-practised and recent songs. No audio is recorded — only the song title and how long the isolation was active.

Practice time earns badges, from Sound Check (1 hour) through Session Player and Touring Musician up to Virtuoso (100 hours). Top achievers appear on the Hall of Fame and the monthly practice leaderboards — anonymously unless you set a display name.

Accounts & privacy

Instrufilt is free, but you sign in once with a free account (Google or GitHub) to use the extension. One account works for both Karafilt and Instrufilt — if you already have a Karafilt account, just sign in with it. All vocal isolation happens locally in your browser — audio is never uploaded. You can delete your account and all associated data at any time from your account page (deleting it deletes it for both products); the details are in the privacy policy.